High demands are raised on materials for cold-work steels, particularly for certain applications, which demands cannot be satisfied satisfactorily with those materials which for the time being are commercially available. This is particular true in connection with applications where abrasive wear is a dominating problem, at the same time as the object shall have an adequate toughness. An application of that kind is for rolls for cold rolling of stainless steel and particularly rolls for the manufacturing of stainless tubes, an application for which the invention has specifically been developed. The invention, however, can be applied also for other types of cold-work steels, as for example for tools for cold-extrusion, powder-pressing, and deep drawing.
A steel grade which today is used for rolls for pilger rolling of stainless tubes is known under its trade name SR1855 and has the nominal composition 0.96 C, 1.50 Si, 0.80 Mn, 1.0 Cr balance iron and impurities in normal amounts. That steel provides an adequate toughness to products like pilger rolls for the manufacturing of stainless tubes. The steel, which is manufactured in a conventional way, however, has an unsatisfying wear resistance and also bad surfaces because of large carbides of M3C-type. An other steel which has been tested for pilger rolls is the steel grade which is powder metallurgical manufactured and which is known under the registered trade mark VANADIS®4 and which has the nominal composition 1.5 C, 1.0 Si, 0.4 Mn, 8.0 Cr, 1.5 Mn, 4.0 V, balance iron and impurities in normal amounts. Also the standardised hot-work steel SS2242 has been used for pilger rolls. That steel has the nominal composition 0.39 C, 1.0 Si, 0.4 Mo, 5.2 Cr, 1.4 Mn, 0.9 V, balance iron and impurities in normal amounts. Further, the standardised high-speed steel M1 is used and also the commercial, powder metallurgical manufactured high-speed steel VANADIS®23, which has the nominal composition 1.28 C, 4.4 CR, 5.0 Mo, 6.4 W, 3.1 V, and normal amounts of Mn, Si and unavoidable impurities. The last mentioned steel has a very good wear resistance but does not provide an adequate toughness to the product. Besides, these steels are comparatively expensive because of their high content of alloying elements, and/or because of the powder metallurgical manufacturing.